This article examines the effect of war events and pre-war depression on the prevalence of major depression during war. A total of 658 subjects aged 18-65 years were randomly selected from four Lebanese communities differentially exposed to the Lebanon Wars and were interviewed using the Diagnostic Interview Schedule (Arabic version). The individual levels of exposure to war events were assessed through a War Events Questionnaire. The lifetime prevalence of the DSM-III-R-defined major depression varied across the four communities from 16.3 to 41.9%; the final parameters predicting major depression since the onset of the wars were: depression before the wars and exposure to the wars. Both, individual levels of exposure to war and a history of pre-war depression, predict the development of depression during war.